Controlling the dynamics of a two-joined arm by central patterning and reflex-like processing. A two-stage hybrid model.

It is demonstrated, that a two-joined arm performing goal directed movements is controllable (a) by two central pattern generators (CPG) representing sampled data control, each referring to one joint, initiated for exactly one period, and producing the angular movement width about this joint, and (b) by reflex-like processes operating continuously with respect to time. The latter eliminate the effects of dynamic coupling, gravity, inertia, and mechanical impedance on the movement by 'proprioceptive feedforward' of position, velocity and acceleration signals, thus enabling the CPGs to handle the arm segments as if they were independent and free from forces. Higher ordered centers (with respect to the CPGs) therefore only need to control the kinematics, not dynamics, of the arm.